Transmission systems use a number of different transmission configurations and control schemes. Such transmissions typically include a plurality of intermeshing gears that are either fixed to transmission shafts or that rotate freely on the shafts. Clutches associated with the freely rotating gears may be selectively engaged to establish a series of speed ratios between a prime mover output shaft and transmission output shaft to transmit torque at a desired speed to drive a machine. Control systems for controlling the clutches typically include electronic circuitry that responds to operator controls such as those directing speed and/or shuttle shifts. The control system may send electrical signals to hydraulic valves that control the clutches. The control system thus causes the clutches to engage and disengage in predetermined combinations to accelerate, decelerate, and drive a machine as desired by the operator.
Some of the control systems provide a directional or shuttle shifting capability that permits an operator to command direct shifting between a forward gear and a reverse gear by movement of a gear shift lever or similar command device directly to the target gear. Various systems have been used in connection with directional or shuttle shifting operations to slow the velocity of the machine during the operation. In general, such systems disengage the clutches corresponding to the then current gear ratio and eventually engage clutches corresponding to the target gear ratio.
U.S. Pat. No. 4,989,470 discloses a system that permits controlled deceleration of a vehicle during shuttle shifts by disengaging the transmission from the engine by disengaging one of the clutches within the transmission. A different clutch is then engaged to create braking or tie-up within the transmission to create a load on the vehicle and slow the rotation of the transmission and the velocity of the vehicle. Once the vehicle has reached a desired velocity, typically close to zero, the clutch used for braking is disengaged and another clutch engaged for accelerating the vehicle in the desired direction.
The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovations described herein nor to limit or expand the prior art discussed. Thus the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use with the innovations described herein, nor is it intended to indicate any element, including solving the motivating problem, to be essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.